The electromomentum effect in piezoelectric Willis scatterers

Materials with asymmetric microstructure can constitutively couple macroscopic fields from different physics. Examples include piezoelectric materials that couple mechanical and electric fields and Willis materials that anomalously couple dynamic and elastic fields. Recently, it was shown anomalous coupling between the elastodynamic and electric field emerges when piezoelectricity is incorporated into Willis materials. Here, we investigate such one-dimensional piezoelectric Willis elements using heuristic homogenization, long-wavelength asymptotic analysis and numerical experiments. We show that an anomalous electromomentum coupling is necessary to explain the scattering properties of the asymmetric piezoelectric media by a macroscopic description that respects reciprocity and energy conservation. Our findings elucidate the origins of the electromomentum coupling and provide insight for the future design of this new class of coupled-field metamaterials.

Contessa perdono! Mozartian sexual betrayal and forgiveness

The dramatic and musical climax of 'The Marriage of Figaro', perhaps Mozart’s operatic masterpiece, is famously marked by the unexpected forgiveness of the Count by the Countess, whom the count has infamously refused to forgive earlier in the opera. This article will explore the musical and psychological ramifications of forgiveness and the refusal to forgive within couple relationships, not only in this opera but also in two other great Mozart operas, 'Don Giovanni' and 'Così fan tutte', in which issues around forgiveness are also implicitly central. It will be argued that Mozart’s very differing and contrasting realisations of this core human and couple dynamic through his unique dramatic, verbal, and musical talents may partially account for the reputation of these operas for depth and universality.

ESCRT-III/Vps4 controls heterochromatin-nuclear envelope attachments

In eukaryotes chromosomes are compartmentalized within the nucleus delimited by the double membrane of the nuclear envelope (NE). Defects in the function and structure of the NE are linked to disease1,2. During interphase, the NE organizes the genome and regulates its expression3. As cells enter mitosis, chromosomes are released from the NE, which is then remodelled to form the daughter nuclei at mitotic exit4. Interactions between the NE and chromatin underpinning both interphase and post-mitotic NE functions are executed by inner nuclear membrane (INM) proteins such as members of the evolutionarily conserved chromatin-binding LEM-domain family5–8. How chromatin tethering by these transmembrane proteins is controlled in interphase and if such a regulation contributes to subsequent NE dynamics in mitosis remains unclear. Here we probe these fundamental questions using an emerging model organism, the fission yeastSchizosaccharomyces japonicus, which breaks and reforms the NE during mitosis9,10. We show that attachments between heterochromatin and the transmembrane Lem2-Nur1 complex are continuously remodelled in interphase by the ESCRT-III/AAA-ATPase Vps4 machinery. ESCRT-III/Vps4 mediates the release of Lem2-Nur1 from heterochromatin as a prerequisite for the timely progression through mitosis. Failure in this process leads to persistent association of chromosomes with the INM, which prevents Lem2-Nur1 from re-localizing to the sites of NE sealing around the mitotic spindle and severely delays re-establishment of nucleocytoplasmic compartmentalization. Our work establishes the INM transmembrane Lem2-Nur1 complex as a ‘substrate’ for ESCRT-III/Vps4 to couple dynamic tethering of chromosomes to the INM with the establishment of nuclear compartmentalization.